Since the past, nitrile rubber (acrylonitrile-butadiene copolymer rubber) has been used as a material for rubber parts such as hoses and tubes for automobiles by taking advantage of its fuel oil resistance, mechanical properties, chemical resistance, etc. Further, hydrogenated nitrile rubber (highly saturated nitrile rubber) obtained by saturation by hydrogenating the carbon-carbon double bonds in the polymer main chain is further excellent in heat resistance, so is being used for rubber parts such as hoses, seal members, gaskets, and diaphragms.
In recent years, the properties demanded for rubber parts for automobiles have become increasingly tough. In particular, rubber parts used for seal member applications, in particular rubber parts used for high pressure seal member applications, have been required to be excellent in compressive stress from the viewpoint of keeping defamation low even under high pressure conditions in addition to excellent heat resistance and fuel oil resistance.
For example, Patent Document 1 discloses a rubber composition obtained by blending a polyamide with a hydrogenated carboxylated nitrile rubber at a temperature over 20° C. According to the art of this Patent Document 1, a cross-linked rubber excellent in heat resistance and fuel oil resistance is obtained, but the compressive stress is not sufficient, therefore this has not been suited for seal member applications, in particular application to high pressure seal members used in high pressure environments.